Cant really use FMU?

Soo I’m on the weirdest sleep schedule 🤦🏾‍♀️ basically goes like this I work usually 4 or 5pm and only work 4-6 hour shifts so when i get off i go home and basically stay up hanging out with my BIL and SO until 5am or 6am the next day and then ill sleep from then to about 3pm and then go to work and do it all again. Its a terrible schedule 😩😩 but I’m now wondering when would my “first morning” urine be? Lmao